<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>TAB</title>
    <link rel="stylesheet" href="tabindex.css">
    <script src="tabindex.js"></script>
</head>
<body>
       <ul class="titles">

        <li class="title active">标题1</li>
        <li class="title ">标题2</li>
        <li class="title ">标题3</li>
       </ul>
        
        
        <ul class="contents">
            <li class="content active">内容1</li>
            <li class="content " >内容2</li>
            <li class="content ">内容3</li>
        </ul>
        <button id="add">添加</button>
        
                    
    
</body>
</html>